This invention relates generally to a composite polypropylene resin article useful as an exterior material, an interior material or a bumper of automobiles and, more particularly, to a composite material having a polypropylene resin molded body to which a polypropylene resin foamed body is fuse-bonded. The present invention is also directed to a method of producing the above composite material.
A polypropylene resin is now used as exterior materials, interior materials and bumpers of automobiles because of its excellent resistance to solvents, low specific gravity, good rigidity, good cost balance and capability of reuse. With regard to bumpers, the recent trend is toward the use of light weight materials for reasons of reduction of fuel consumption. Thus, there is a great demand for bumpers having a reduced weight and, yet, high mechanical strengths, especially good shock absorbing properties.
JP-A-H5-13874 discloses a five-layered bumper composed of a core of a foamed polypropylene resin molded body interposed between and fuse-bonded to a pair of polypropylene resin layers with fusible adhesive layers. The use of adhesive layers causes increased production costs and prevents recycled uses of the polypropylene resin.
JP-A-H9-39019 discloses a bumper composed of a polypropylene resin hollow molded body and a foamed resin core provided within the hollow molded body. The core is formed by foaming expanded resin particles within the hollow space of the molded body so that the core is fuse-bonded to the hollow molded body. This bumper has problems, however, because of a difficulty to produce the hollow molded body and because of a weak bonding between the core and the molded body.